This proposal deals with a number of issues in the study of semantic memory. One concern is with the nature of semantic representations for words, and how they are processed when one must decide whether a statement about category membership (like A robin is a bird) is True or False. Our experiments will deal with the effects of instance-category semantic similarity on the speed of True decisions, and with the effects of contradictions on the speed of False decisions. A second issue for study is how one combines semantic representations for words into larger meaning units. To get at this, we will perform studied in which subjects are timed while they verify statements containing multiple propositions (e.g., A robin has a blue breast). Such studies should tell us something about the order in which one combines the component propositions of a complex sentence. A third issue of concern is how one interrelates semantic and perceptual representations. We will time subjects while they decide whether or not a word (e.g., fruit) is a true description of a pictured object (e.g., a pictured apple). Such studies should provide evidence about whether one compares a picture and a word by first translating both into a common semantic code. BIBLIOGRAPHIC REFERENCES: Smith, E.E., Haviland, S.E., Reder, L.M., Brownell, H., and Adams, N. When preparation fails: Disruptive effects of prior information on perceptual recognition. Journal of Experimental Psychology: Human Performance and Perception, 1976, 2, 151-161. Herrmann, D.J., Shoben, E.J. Klun, J.R., and Smith, E.E. Cross-category structure in semantic memory. Memory and Cognition, 1975.